﻿<p>A curtain wall is an exterior wall of a building which is
an assembly of components, hung from the edge of the floor/roof
structure rather than bearing on a floor. Curtain wall is
represented as a building element assembly and implemented as a
subtype of <em>IfcBuildingElement</em> that uses an
<em>IfcRelAggregates</em> relationship.</p>
<blockquote class="extDef">NOTE&nbsp; Definition according to ISO 6707-1: 
non load bearing wall positioned on the outside of a building and enclosing it.</blockquote>

<blockquote class="history">HISTORY&nbsp; New entity in IFC2.0</blockquote>

<p>The geometric representation of <em>IfcCurtainWall</em> is given by the <em>IfcProductDefinitionShape</em>, allowing multiple
geometric representations. Independent 'Body' geometric representation, as described below, should only be used when the
<em>IfcCurtainWall</em> is not defined as an aggregate. If defined as an aggregate, the geometric representation is the sum of the
representations of the components within the aggregate.</p>

<p>The geometric representation of <em>IfcCurtainWall</em> is defined using the following multiple shape representations for
its definition:</p>
<ul>
<li>Axis: A two-dimensional open curve (for restrictions see below) defining the axis for the curtain wall.
<ul>
<li>This is an optional representation for curtain walls.</li>
</ul>
</li>
<li>Body: A surface model or boundary representation model representation defining the 3D shape of the curtain wall.
<ul>
<li>If the <em>IfcCurtainWall</em> has components (referenced by <em>SELF\IfcObject.IsDecomposedBy</em>) then no independent shape
representation with <em>RepresentationType</em> = 'Body' shall be defined. The body of <em>IfcCurtainWall</em> is then geometrically
represented by the shape representation of its components. The components are accessed via
<em>SELF\IfcObject.IsDecomposedBy[1].RelatedObjects</em>.</li>
</ul>
<ul>
<li>If the <em>IfcCurtainWall</em> has no components defined (empty set of <em>SELF\IfcObject.IsDecomposedBy</em>) then the
<em>IfcCurtainWall</em> may be represented by an shape representation with the <em>RepresentationIdentifier</em> ='Body'.</li>
</ul>
</li>
</ul>